U/Pb and 207Pb/206Pb ages on detrital zircons, from Quartzite El Quemado (Caucete Group), Pie de Palo range, San Juan Province

NAIPAUER MAXIMILIANO; MCCLELLAND WILLIAMS; VUJOVICH GRACIELA IRENE; CINGOLANI CARLOS ALBERTO; ELLIS JOSHUA

La Plata, Argentina.

Congreso; XVI Congreso Geológico Argentino; 2005

Asociación Geológica Argentina.

The Caucete Group is a low-grade metasedimentary sequence comprising an association of siliciclastic and carbonate rocks which is exposed on the western flank of the Pie de Palo range. Two samples from the El Quemado Quartzite exposed at Quebrada La Petaca (31°27´23´´S / 68°10´36´´W) were analyzed for detrital zircons. We present preliminary results on the morphology and U/Pb ages obtained by the LA-ICP-MS method on detrital zircons. The data defines the maximum depositional age at ca. 550 Ma and indicate a significant supply from Mesoproterozoic sources similar to the provenance interpreted for the Cerro Totora Formation earlier. This observation supports the models in which the Caucete Group is part of the Precordillera-Cuyania terrane and was deposited on the Mesoproterozoic crust, like the Grenville and Granite-Rhyolite province in the southeastern sector of Laurentia. Ties to Mesoproterozoic crust of Amazonia are more difficult to explain, especially from a sedimentological view point, as the Sunsas and Rondonian-San Ignacio provinces located thousands of kilometers from the Cuyania paleo-position to the north. Following the allochthonous hypothesis, the provenance of the Neoproterozoic-Cambrian zircons could also be a relationship with a Laurentian source, probably with rocks generated during successive pulses of rifting of the Rodinia supercontinent.